What is merit all about?

I was newly introduced into the system by a friend who made me to have so much interest in the system with the zeal and the passion to learn and gain adequate experience on the system but one of the major problem I’m having now is that I’m not well clarify of what merit entails and as such I will be very grateful if any good minded person can kindly throw more light on that to enable me understand in details and also benefit from the system.